As March turned into April, it was time for me to go exploring again. My destination? Sofia, the capital of Bulgaria: a new city for me and the 49th country I've visited. During my four-day trip, I learned a great deal about Sofia's complex and fascinating history, admired striking and diverse architecture, took several excellent tours with passionate locals and ate delicious food. I even managed a side trip to a UNESCO-listed monastery perched high in the Rila mountains and to the city of Plovdiv. Read on to find out all of my recommendations for spending a long weekend in Plovdiv.